Microphysical variation of precipitation traveling inward along the principal rainband of typhoon <i>Ampil</i> (2018)

Abstract Coastal areas are frequently hit by tropical cyclones (TCs), causing loss of life and property. Previous studies have identified that heavy rain events in coastal areas were mainly caused by TC rainbands rather than the rapidly dissipating eyewalls. For example, the quasi‐stationary and long‐lasting principal rainband relative to the TC vortex is more capable of producing persistent localized heavy precipitation. Unlike previous studies that focused on the thermodynamic structure in the rainbands of TCs, this study investigates the microphysical characteristics and their impact on the distribution of intense precipitation in a principal rainband of typhoon Ampil (2018). Using polarimetric radar observations, a size‐sorting radar signature was found inward along the principal rainband of Ampil . In detail, larger (smaller) average differential reflectivity Z DR (specific differential phase K DP ) was evident in the upwind zone. The largest K DP and a maximum of horizontal reflectivity Z H (indicating heavy precipitation) were located in the transition zone, while the smallest values of the three polarimetric variables were observed in the downwind zone. The evolution of dynamics and convection along the principal rainband was discussed to explain the microphysical differences in various portions of the principal rainband and the reason why the most intense precipitation occurred in the transition zone.